05 duramax LLY lack of power

i have an 2005 siverado 3500 duramax, bought it new has around 140,000 miles, for the past few years it seems like the motor is restricted, it has multiple codes, one was over boost, replace that part which was difficult, that didn't work. The symptoms are at an idie it rumbles then spooling, when I first start driving it is sluggish and takes a while to shift, once the motor warms up if I get on the throttle it surges with back pressure so I let off on the throttle, if I am driving and it's under a load and release the petal it has turbo barking. It's at a friend that is a mechanic house and he is troubleshooting the problems, one of his comment he said possibly the vane position sensor? He check the plunger to check if the vanes were stuck and said it slides in and out smoothly.

i forgot to mention it has a edge cts programmer, 4" turbo back straight pipe, an intake and a exhaust brake, when I put all of the things on it never had any problems, then all of a sudden it started getting the symptoms listed above, I can drive it around but have to baby it but when I pull a trailer or my boat it is gutless, I live in Hawaii on the big island and there are not many people that know how to work on duramax.

My programmer shows the vane at 0%, called So Cal Diesel and the said it most likely the vane position sensor, I ordered a new one yesterday and it should be in early next week, I have someone to install it and hook it up to Tect 2 to have it re learned, keep you posted.